For a portable device, power consumption is a key design factor. More particularly, for portable and wearable devices that uses high intensity light for treatment, for example from high power LEDs, battery consumption is even more important, because the high intensity light requires considerable power. Moreover, such a portable device must be able to meet such high power requirements for longer periods of time during subsequent application sessions of light therapy without recharging. In addition, in order to make the device wearable, these requirements must be fitted in a small form factor.
In a number of light therapy treatments, it is effective to activate bodily processes that trigger vasodilation. Vasodilation is part of the body thermo regulatory system and is considered beneficial for wound healing, pain relief, and dermal health.
A further problem of light therapy devices that treat, for instance, muscle pain using light, is that light source produce heat. In prior art, this problem is solved by using heat sinking as, e.g., in U.S. Pat. No. 6,290,713 where the illuminator is passively or actively cooled, so that the skin contact surface remains below a desired temperature. A passive cooling is presented as a fin positioned to provide increased transfer of heat produced by the LEDs away from the skin of the patient. To further protect the patient from the heat produced by the LED light source, U.S. 2010/179469 uses an insulation layer between the portion adapted to contact the skin of a patient and the light source. U.S. 2010/179469 further suggests adjusting the heat using a heat management system to prevent overheating of the patient, for example, by increasing a coolant supply or the speed of a fan.
To some extent, power consumption of light therapy devices may be reduced by pulsing the LED instead of continuously driving the LED, while still creating an effect of vasodilation production, since vasodilation is activated via heat receptors located in the skin which may be triggered by a relatively short, but powerful burst of light. Once it is activated, it will remain active for a relatively long period of time, in the order of several minutes, without the need for further heat stimulus. However, another problem may appear because the user may experience the periods between light pulses as cold, making the device uncomfortable to use.